1. Field of the Invention
The present invention relates generally to computer security, and more particularly but not exclusively to methods and apparatus for filtering computer network traffic.
2. Description of the Background Art
Computers coupled to the Internet may access websites to view various kinds of information. The websites, which are hosted on web servers, include one or more web pages that may be displayed on a web browser of a user's client computer. Each web page has a corresponding network address, commonly referred to as a URL (uniform resource locator), that allows a web browser to locate the web page. The web browser may be pointed to the URL to render the web page on the browser for viewing by the user.
URL filtering involves monitoring of URLs to identify those that belong to prohibited websites (or any content). The websites may be prohibited by policy or other reasons. For example, a corporate computer network may prevent viewing of web pages from pornography websites. In that case, a URL filter may be configured to block URLs belonging to pornography websites. When a web browser attempts to access one of the blocked pornography websites, the URL filter will recognize the URL and block the access.
URL filtering may be performed at a gateway of a computer network. The gateway may perform URL filtering by consulting a web reputation service or other database with information about the URL. Because this consultation or process of finding information about a URL takes time, previously obtained URL information is typically cached for improved performance. Embodiments of the present invention pertain to a caching scheme for URL filtering, and similar applications, for improved user experience in a multi-user computing environment.